Certain embodiments of the present invention are directed to computer technology. More particularly, some embodiments of the invention provide systems and methods for signal processing. Merely by way of example, some embodiments of the invention have been applied to audio signals. But it would be recognized that the invention has a much broader range of applicability.
With the development of voice communication technology, voice communication over the Internet has become increasingly popular. During voice communication between two parties, audio signals are often transmitted by a sender over the network to a receiver, and output from an audio-playback device. Such audio signals often propagate through air to an audio-acquisition device of the receiver, and are sent back to the sender together with audio signals generated by the receiver. Then a user using the sender can hear his/her own voice which corresponds to echoes generated during voice communication. To improve the quality of voice communication, echo reduction often needs to be performed.
Currently, echo reduction usually includes: audio data 1 transmitted by the sender at a current time is received by the receiver and a copy of the audio data 1 is made. The audio data 1 is output from the audio-playback device to generate an audio signal A1. The audio-acquisition device of the receiver acquires at the current time audio signals which include an audio signal B related to a user's voice and another audio signal A2 output from the audio-playback device. Audio data 2 are generated based on the acquired audio signals. Echo reduction is performed on the audio data 2 based on the copy of the audio data 1 to generate audio data 3. Usually, there is a delay for audio signals to propagate through air from the audio-playback device to the audio-acquisition device. In addition, the audio-playback device and the audio-acquisition device are associated with some delay factors. The audio signal A2 corresponds to an audio signal output previously from the audio-playback device before the current time. That is, the audio signal A2 corresponds to an audio signal output from the audio-playback device before the audio signal A1.
The above-noted conventional technology has some disadvantages. For example, as the audio signal A2 corresponds to an audio signal output from the audio-playback device before the audio signal A1, the audio data 3 generated by performing echo reduction on the audio data 2 based on the copy of the audio data 1 may still include echoes, no as to reduce the echo-reduction efficiency.
Hence it is highly desirable to improve the techniques for echo reduction.